Thiocyanogen: Its Spectra and Heat of Formation in Relation to Structure

Vanderzee, Cecil E.; Quist, Arvin S.

doi:10.1021/ic50041a036

Cited by 32 publications

(12 citation statements)

References 6 publications

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“…The Raman spectrum shows bands at 2158, 668, 494, and 397 cm -1 corresponding to ν (C⋮N), ν (C−S), ν (S−S), and δ (S−C⋮N), respectively. These observations are in accord with the literature IR and Raman data, , and our observed data are modeled well by the calculations. The single resonances in both the 13 C{ 1 H} and 14 N NMR spectra show that there is only one carbon and one nitrogen environment in the molecule.…”

Section: Resultssupporting

confidence: 92%

E₂(CN)₂ (E = S, Se) and Related Compounds

Burchell¹,

Kilián²,

Slawin³

et al. 2005

Inorg. Chem.

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Section: Resultssupporting

confidence: 92%

E₂(CN)₂ (E = S, Se) and Related Compounds

Burchell¹,

Kilián²,

Slawin³

et al. 2005

Inorg. Chem.

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“…From these reactions, it is calculated that Δ H f o ((SCN) 2 ( g )) = 378 ± 14 kJ/mol. This calculated value of Δ H f o ((SCN) 2 ( g )) is quite different from the experimental value (344 kJ/mol) . It is unclear whether this difference is the result of some aspect of the computational technique used or difficulties in the experimental determination.…”

Section: Discussioncontrasting

confidence: 56%

“…This value can be used to derive the free energy of solvation of (SCN) 2 from the experimental enthalpy of formation of (SCN) 2 ( g ) reported by Vanderzee and Quist: Δ H f o ((SCN) 2 ( g )) = 344 kJ/mol . On the basis of entropy values reported in the NBS tables for molecules of similar size, the value of S °((SCN) 2 ( g )) can be estimated to be 300 (± 50) J/(mol K).…”

Section: Discussionmentioning

confidence: 99%

Acidic Aqueous Decomposition of Thiocyanogen

2004

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The aqueous reaction of acidic Cl2 with excess SCN- rapidly generates a UV-absorbing intermediate identified as an equilibrium mixture of thiocyanogen, (SCN)2, and trithiocyanate, (SCN)3(-). The decomposition of this mixture can be described as 3(SCN)2 + 4H2O --> 5HSCN + H2SO4 + HCN. Under our conditions the decomposition is sufficiently slow that its kinetics can be studied using standard stopped-flow methodology. Over the pH range 0-2 the decomposition rate law is -d[(SCN)2]/dt = (3/2)[k(disp)K(hyd)2[(SCN)2]2/([SCN-]2[H+]2 + K(SCN)3-[SCN-]3[H+]2 + K(hyd)[SCN-][H+])] with K(SCN)3(-) = 0.43 +/- 0.29 M(-1), K(hyd) = (5.66 +/- 0.77) x 10(-4) M2, and k(disp) = (6.86 +/- 0.95) x 10(4) M(-1) s(-1) at 25 degrees C and micro = 1 M. The K(SCN)3(-) and K(hyd) terms are significant enhancements relative to one of the rate laws conventionally cited. In the proposed mechanism, K(SCN)3(-) refers to the formation of (SCN)3(-) by association of SCN- with (SCN)2, K(hyd) refers to the hydrolysis of (SCN)2 to form HOSCN, and k(disp) is the rate constant for the bimolecular irreversible disproportionation of HOSCN, which leads ultimately to SO4(2-) and HCN. Ab initio calculations support the values of K(SCN)3(-) and K(hyd) reported herein. The high value for k(disp) indicates that HOSCN is a short-lived transient, while the magnitude of K(hyd) provides information on its thermodynamic stability. These results bear on the physiological role of enzymes that catalyze the oxidation of SCN- such as salivary peroxidase and myeloperoxidase.

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“…If dissociation of phenanthroline occurred during the reaction, substitution of SCN-into the first coordination sphere of the Fe(II1) complex might be expected to occur to give Fe(III)phen,(SCN), which was reported to be a dark red solid (8). Although oxidation of SCN-by Fe(II1) in acetonitrile produced (SCN), (9), we are not surprised that CN-and SO4'-are the oxidation products since (SCN), is known to decompose readily in aqueous medium (10). Oxidation of SCN-by Fe-(H20)63+ (11) and H,O, (12) in acidic medium was reported to produce CN-and SO4'-.…”

Section: Variation Of K" With the Reduction Potentialmentioning

confidence: 87%

Kinetics and Mechanism of the Oxidation of Thiocyanate by Tris(1,10-phenanthroline)iron(III) and its Derivatives

Ng¹,

Henry²

1975

Can. J. Chem.

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. Can. J. Chem. 53,3319 (1975). Oxidation of thiocyanate by tris(1 ,lo-phenanthroline)Fe(III) to give cyanide and sulfate ions was studied at 25 "C in both H2S04 and HC104 media. The rate of oxidation showed a first order dependence on the Fe(II1) complex and a second order dependence on potassium thiocyanate at 24.0 x M potassium thiocyanate. The value of k,,, decreased with increasing [H+]. This acid inhibition is consistent with the protonation of SCN-to give an inactive HSCN species. A mechanism consistent with the data involved an initial equilibrium formation of [Fephen3SCNI2+ which subsequently undergoes an outer-sphere electron transfer with SCNto eventually give Fe(II)phen,, CN-, and Sod2-. Similar kinetic behavior was found with the substituted tris(1 ,lo-phenanthroline)Fe(III)complexes. Thevalue of the third order rateconstant was found to increase with the increase in the reduction potential of the complexes. This result indicates a direct dependence of the standard free energy of the reaction and the free energy of activation. [Traduit par le journal]

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Thiocyanogen: Its Spectra and Heat of Formation in Relation to Structure

Cited by 32 publications

References 6 publications

E₂(CN)₂ (E = S, Se) and Related Compounds

E₂(CN)₂ (E = S, Se) and Related Compounds

Acidic Aqueous Decomposition of Thiocyanogen

Kinetics and Mechanism of the Oxidation of Thiocyanate by Tris(1,10-phenanthroline)iron(III) and its Derivatives

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Thiocyanogen: Its Spectra and Heat of Formation in Relation to Structure

Cited by 32 publications

References 6 publications

E2(CN)2 (E = S, Se) and Related Compounds

E2(CN)2 (E = S, Se) and Related Compounds

Acidic Aqueous Decomposition of Thiocyanogen

Kinetics and Mechanism of the Oxidation of Thiocyanate by Tris(1,10-phenanthroline)iron(III) and its Derivatives

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Product

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E₂(CN)₂ (E = S, Se) and Related Compounds

E₂(CN)₂ (E = S, Se) and Related Compounds